C++ DiffContext::elem_reinit方法代码示例

bool EulerSolver::element_residual (bool request_jacobian,
                                    DiffContext &context)
{
    unsigned int n_dofs = context.get_elem_solution().size();

    // Local nonlinear solution at old timestep
    DenseVector<Number> old_elem_solution(n_dofs);
    for (unsigned int i=0; i != n_dofs; ++i)
        old_elem_solution(i) =
            old_nonlinear_solution(context.get_dof_indices()[i]);

    // Local nonlinear solution at time t_theta
    DenseVector<Number> theta_solution(context.get_elem_solution());
    theta_solution *= theta;
    theta_solution.add(1. - theta, old_elem_solution);

    // Technically the elem_solution_derivative is either theta
    // or -1.0 in this implementation, but we scale the former part
    // ourselves
    context.elem_solution_derivative = 1.0;

// Technically the fixed_solution_derivative is always theta,
// but we're scaling a whole jacobian by theta after these first
// evaluations
    context.fixed_solution_derivative = 1.0;

    // If a fixed solution is requested, we'll use theta_solution
    if (_system.use_fixed_solution)
        context.get_elem_fixed_solution() = theta_solution;

    // Move theta_->elem_, elem_->theta_
    context.get_elem_solution().swap(theta_solution);

    // Move the mesh into place first if necessary
    context.elem_reinit(theta);

    // We're going to compute just the change in elem_residual
    // (and possibly elem_jacobian), then add back the old values
    DenseVector<Number> old_elem_residual(context.get_elem_residual());
    DenseMatrix<Number> old_elem_jacobian;
    if (request_jacobian)
    {
        old_elem_jacobian = context.get_elem_jacobian();
        context.get_elem_jacobian().zero();
    }
    context.get_elem_residual().zero();

    // Get the time derivative at t_theta
    bool jacobian_computed =
        _system.element_time_derivative(request_jacobian, context);

    // For a moving mesh problem we may need the pseudoconvection term too
    jacobian_computed =
        _system.eulerian_residual(jacobian_computed, context) && jacobian_computed;

    // Scale the time-dependent residual and jacobian correctly
    context.get_elem_residual() *= _system.deltat;
    if (jacobian_computed)
        context.get_elem_jacobian() *= (theta * _system.deltat);

    // The fixed_solution_derivative is always theta,
    // and now we're done scaling jacobians
    context.fixed_solution_derivative = theta;

    // We evaluate mass_residual with the change in solution
    // to get the mass matrix, reusing old_elem_solution to hold that
    // delta_solution.  We're solving dt*F(u) - du = 0, so our
    // delta_solution is old_solution - new_solution.
    // We're still keeping elem_solution in theta_solution for now
    old_elem_solution -= theta_solution;

    // Move old_->elem_, theta_->old_
    context.get_elem_solution().swap(old_elem_solution);

    // We do a trick here to avoid using a non-1
    // elem_solution_derivative:
    context.get_elem_jacobian() *= -1.0;
    context.fixed_solution_derivative *= -1.0;
    jacobian_computed = _system.mass_residual(jacobian_computed, context) &&
                        jacobian_computed;
    context.get_elem_jacobian() *= -1.0;
    context.fixed_solution_derivative *= -1.0;

    // Move elem_->elem_, old_->theta_
    context.get_elem_solution().swap(theta_solution);

    // Restore the elem position if necessary
    context.elem_reinit(1.);

    // Add the constraint term
    jacobian_computed = _system.element_constraint(jacobian_computed, context) &&
                        jacobian_computed;

    // Add back the old residual and jacobian
    context.get_elem_residual() += old_elem_residual;
    if (request_jacobian)
    {
        if (jacobian_computed)
            context.get_elem_jacobian() += old_elem_jacobian;
        else
//.........这里部分代码省略.........

bool Euler2Solver::element_residual (bool request_jacobian,
                                     DiffContext &context)
{
  unsigned int n_dofs = context.elem_solution.size();

  // Local nonlinear solution at old timestep
  DenseVector<Number> old_elem_solution(n_dofs);
  for (unsigned int i=0; i != n_dofs; ++i)
    old_elem_solution(i) =
      old_nonlinear_solution(context.dof_indices[i]);

  // We evaluate mass_residual with the change in solution
  // to get the mass matrix, reusing old_elem_solution to hold that
  // delta_solution.
  DenseVector<Number> delta_elem_solution(context.elem_solution);
  delta_elem_solution -= old_elem_solution;

  // Our first evaluations are at the true elem_solution
  context.elem_solution_derivative = 1.0;

  // If a fixed solution is requested, we'll use the elem_solution
  // at the new timestep
  if (_system.use_fixed_solution)
    context.elem_fixed_solution = context.elem_solution;

  context.fixed_solution_derivative = 1.0;

  // We're going to compute just the change in elem_residual
  // (and possibly elem_jacobian), then add back the old values
  DenseVector<Number> total_elem_residual(context.elem_residual);
  DenseMatrix<Number> old_elem_jacobian, total_elem_jacobian;
  if (request_jacobian)
    {
      old_elem_jacobian = context.elem_jacobian;
      total_elem_jacobian = context.elem_jacobian;
      context.elem_jacobian.zero();
    }
  context.elem_residual.zero();

  // First, evaluate time derivative at the new timestep.
  // The element should already be in the proper place
  // even for a moving mesh problem.
  bool jacobian_computed =
    _system.element_time_derivative(request_jacobian, context);

  // For a moving mesh problem we may need the pseudoconvection term too
  jacobian_computed =
    _system.eulerian_residual(jacobian_computed, context) && jacobian_computed;

  // Scale the new time-dependent residual and jacobian correctly
  context.elem_residual *= (theta * _system.deltat);
  total_elem_residual += context.elem_residual;
  context.elem_residual.zero();

  if (jacobian_computed)
    {
      context.elem_jacobian *= (theta * _system.deltat);
      total_elem_jacobian += context.elem_jacobian;
      context.elem_jacobian.zero();
    }

  // Next, evaluate the mass residual at the new timestep,
  // with the delta_solution.
  // Evaluating the mass residual at both old and new timesteps will be
  // redundant in most problems but may be necessary for time accuracy
  // or stability in moving mesh problems or problems with user-overridden
  // mass_residual functions

  // Move elem_->delta_, delta_->elem_
  context.elem_solution.swap(delta_elem_solution);

  jacobian_computed = _system.mass_residual(jacobian_computed, context) &&
    jacobian_computed;

  context.elem_residual *= -theta;
  total_elem_residual += context.elem_residual;
  context.elem_residual.zero();

  if (jacobian_computed)
    {
      // The minus sign trick here is to avoid using a non-1
      // elem_solution_derivative:
      context.elem_jacobian *= -theta;
      total_elem_jacobian += context.elem_jacobian;
      context.elem_jacobian.zero();
    }

  // Add the time-dependent term for the old solution

  // Make sure elem_solution is set up for elem_reinit to use
  // Move delta_->old_, old_->elem_
  context.elem_solution.swap(old_elem_solution);

  // Move the mesh into place first if necessary
  context.elem_reinit(0.);

  if (_system.use_fixed_solution)
    {
      context.elem_solution_derivative = 0.0;
      jacobian_computed =
//.........这里部分代码省略.........